The use of quadrature amplitude modulation ("QAM") and vestigial sideband ("VSB") modulation for transmitting data, such as high definition television ("HDTV") signals, is growing in popularity.
In the United States, HDTV systems, which include, e.g., Advanced television ("ATV") systems, appear to be headed in two different directions with regard to the type of modulation used to transmit television signals.
At present, cable companies in the United States are preparing to transmit HDTV digital signals over cable using a QAM technique of data transmission.
On the other hand, the terrestrial television industry in the U.S. is planning to broadcast digital HDTV, e.g., ATV signals, using a Vestigial SideBand ("VSB") technique of data transmission proposed by Zenith corporation/Grand Alliance.
Accordingly, to be capable of receiving and displaying both cable and terrestrial HDTV television transmissions, a television receiver will have to be capable of receiving and demodulating both QAM and VSB HDTV signals.
Because equalizer circuitry constitutes a major component of a demodulator, there is therefor a need for equalizer circuitry that can be used as part of a demodulator for demodulating either QAM or VSB signals.
Furthermore, so that the equalizer can be implemented at a reasonable cost, it is highly desirable that such an equalizer be capable of being implemented using a single common set of hardware that is used in both QAM and VSB modes of operation.